diff -r 65d07d9ee446 -r 8e47bac5643a src/share/vm/oops/instanceOop.hpp
--- a/src/share/vm/oops/instanceOop.hpp	Mon Oct 08 17:04:00 2012 -0700
+++ b/src/share/vm/oops/instanceOop.hpp	Tue Oct 09 10:11:38 2012 +0200
@@ -37,7 +37,9 @@
 
   // If compressed, the offset of the fields of the instance may not be aligned.
   static int base_offset_in_bytes() {
-    return UseCompressedKlassPointers ?
+    // offset computation code breaks if UseCompressedKlassPointers
+    // only is true
+    return (UseCompressedOops && UseCompressedKlassPointers) ?
              klass_gap_offset_in_bytes() :
              sizeof(instanceOopDesc);
   }